The invention relates to a sewing machine having an optical detector.
Optical detectors are used on sewing machines for example to detect one or more layers of workpieces and in particular to detect the edges of workpieces. A preset evaluating device triggers control commands to the sewing machine control which can, for example, be used to operate a cutter or to terminate the sewing process.
An optical detector on a sewing machine to detect an edge of a workpiece is known from the German Offenlegungsschrift DE 35 19 729 Al. A light source arranged above the sewing level radiates a narrow-band frequency spectrum which is directed from the working area to an opto-electrical sensor by way of a separate light wave conductor, an evaluating device being inserted after the sensor. It is true that this solution is considerably independent from the basic construction of a sewing machine; it does, however, demand that a light wave conductor be attached in the work area, e.g. on the sewing machine table designed as a plate. Furthermore loss of light can occur in the light wave conductor.
An object of the invention is therefore to develop an optical detector comprising a light transmitter and a light receiver, so that light loss is avoided as much as possible and so that it is possible to install and remove the needle plate in a simple manner.